Battery assembly for medical device

ABSTRACT

In some examples, a battery assembly for an implantable medical device. The battery assembly may include an electrode stack comprising a plurality of electrode plates, wherein the plurality of electrode plates comprises a first electrode plate including a first tab extending from the first electrode plate and a second electrode plate including a second tab extending from the second electrode plate; a spacer between the first tab and the second tab; and a rivet extending through the first tab, second tab, and spacer, wherein the rivet is configured to mechanically attach the first tab, second tab, and spacer to each other.

This application claims the benefit of U.S. Provisional PatentApplication No. 62/835,738, filed Apr. 18, 2019, the entire content ofwhich is incorporated herein by reference.

TECHNICAL FIELD

The disclosure relates to batteries and, more particularly, to batteriesof medical devices.

BACKGROUND

Medical devices such as implantable medical devices (IMDs) include avariety of devices that deliver therapy (such as electrical simulationor drugs) to a patient, monitor a physiological parameter of a patient,or both. IMDs typically include a number of functional componentsencased in a housing. The housing is implanted in a body of the patient.For example, the housing may be implanted in a pocket created in a torsoof a patient. The housing may include various internal components suchas batteries and capacitors to deliver energy for therapy delivered to apatient and/or to power circuitry for monitoring a physiologicalparameter of a patient and controlling the functionality of the medicaldevice.

SUMMARY

In some aspects, the disclosure is directed to battery assemblies foruse, e.g., in a medical device, and techniques for manufacturing thebattery assemblies.

In one example, the disclosure is directed to a battery assembly for animplantable medical device. The assembly may comprise an electrode stackcomprising a plurality of electrode plates, wherein the plurality ofelectrode plates comprises a first electrode plate including a first tabextending from the first electrode plate and a second electrode plateincluding a second tab extending from the second electrode plate; aspacer between the first tab and the second tab; and a rivet extendingthrough the first tab, second tab, and spacer, wherein the rivet isconfigured to mechanically attach the first tab, second tab, and spacerto each other. In another example, the disclosure is directed to animplantable medical device comprising such a battery assembly within anouter housing of the implantable medical device, and processingcircuitry, wherein the processing circuitry is configured to controldelivery electrical therapy from the implantable medical device to apatient using power supplied by the battery assembly.

In another example, the disclosure is directed to a battery assembly foran implantable medical device. The assembly may comprise a batteryhousing; an electrode stack comprising a plurality of electrode plates,wherein the plurality of electrode plates including a first tab stack ofanode tabs extending from anode plates of the electrode stack and asecond tab stack of cathode tabs extending from cathodes plates of theelectrode stack, wherein the first tab stack is adjacent to the secondtab stack and a gap separates the first tab stack from the second tabstack; and a shim located on a top tab of at least one of the first tabstack or the second tab stack, wherein the shim is located between theat least one of the first tab stack or the first tab of the second tabstack and the battery housing. In another example, the disclosure isdirected to an implantable medical device comprising such a batteryassembly within an outer housing of the implantable medical device, andprocessing circuitry, wherein the processing circuitry is configured tocontrol delivery electrical therapy from the implantable medical deviceto a patient using power supplied by the battery assembly.

The details of one or more examples of the disclosure are set forth inthe accompanying drawings and the description below. Other features,objects, and advantages of the disclosure will be apparent from thedescription and drawings, and from the claims.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a conceptual diagram that illustrates an example medicaldevice system that may be used to deliver therapy to a patient.

FIG. 2 is a conceptual diagram illustrating a partial exploded view ofthe IMD of FIG. 1.

FIGS. 3 and 4 are conceptual diagrams illustrating portions of anexample battery assembly in accordance with examples of the disclosure.

FIG. 5 is a conceptual diagram illustrating a portion of an examplebattery assembly including a stack of tabs and spacers of an electrode.

FIG. 6 is a conceptual diagram illustrating a cross-sectional view ofthe stack of tabs and spacers of FIG. 5.

FIG. 7 is a conceptual diagram illustrating an example rivet that may beincluded in a battery assembly.

FIG. 8 is a conceptual diagram illustrating an example assembly forforming a battery assembly including a rivet.

FIG. 9 is a flowchart illustrating an example technique in accordancewith examples of the disclosure.

FIG. 10 is a conceptual diagram illustrating a portion of an examplebattery assembly in accordance with examples of the disclosure.

FIG. 11 is a conceptual diagram illustrating the example shim shown inFIG. 10.

FIG. 12 is a conceptual diagram illustrating the example batteryincluding an example shim.

DETAILED DESCRIPTION

A variety of medical devices may utilize one or more batteries as apower source for operational power. For example, an implantable medicaldevice (IMD) that provides cardiac rhythm management therapy to apatient may include a battery to supply power for the generation ofelectrical therapy or other functions of the IMD. For ease ofillustration, examples of the present disclosure will be describedprimarily with regard to batteries employed in IMDs that provide cardiacrhythm management therapy. However, as will be apparent from thedescription herein, examples of the disclosure are not limited to IMDsthat provide such therapy. For example, in some instances, one or moreof the example batteries describe herein may be used by a medical deviceconfigured to deliver electrical stimulation to a patient in the form ofneurostimulation therapy (e.g., spinal cord stimulation therapy, deepbrain stimulation therapy, peripheral nerve stimulation therapy,peripheral nerve field stimulation therapy, pelvic floor stimulationtherapy, and the like). In some examples, example batteries of thisdisclosure may be employed in medical device configured to monitor oneor more patient physiological parameters, e.g., by monitoring electricalsignals of the patient, alone or in conjunction with the delivery oftherapy to the patient.

In some examples, a battery of an IMD may include a plurality ofelectrode plates (e.g., including both anode and cathode plates) stackedon each other in which each of the plates includes a tab extendingtherefrom. The tabs of the anode plates may be aligned with each otherin a stack and electrically connected to each other to form an anode ofthe battery. In this sense, the tab stack may function as an electricalinterconnect between the plates of the anode. Similarly, the tabs of thecathode plates may be aligned with each other in a stack andelectrically connected to each other to form a cathode of the battery.In some examples, such a battery may be referred to as a flat platebattery.

In some examples, in each the anode tab stack and cathode tab stack, aspacer may be located between adjacent individual tabs in the stack oftabs, e.g., such that each individual tab is separated from an adjacenttab by a spacer. The spacers may be electrically conductive toelectrically couple the respective tabs in the stack to each other anddefine an electrical interconnect, at least in part, between respectiveplates of the electrode. For each electrode, the tabs in the stack oftabs and spacers may be attached to each other by one or more side laserwelds that span the height of the tab stack.

In some examples, the tabs of an electrode stack may be flexed or bentdue to the nature of the spacer and tab interconnect design. Thisresults in stressed materials that can lead to failures of the sideweld(s) and/or insulation failures.

In some examples, a stacked plate battery interconnect spacer stack maybe subject to “fanning” (e.g., opening like the pages of a bound book)as a result of the mechanical force applied by the expansion of theelectrode stack, e.g., during discharge of the battery. The appliedforce may displace the spacer stack causing electrical shorting to thesurrounding battery enclosure, and/or leading to failure of the laserwelds on the interconnect spacer stack.

In some examples, the laser welds on the side of an interconnect spacerstack are subject to mechanical loading, e.g., when the electrode stackexpands during battery life. The electrode stack expansion may be due toplate warp or cathode expansion during battery discharge. As describedabove, the mechanical loading on the interconnect spacer stack mayresult in the interconnect spacer stack “fanning” open much like when abook and its many pages are opened.

In accordance with at least some examples of the disclosure, a batteryassembly that includes an electrode tab stack may include spacers ofvarying thicknesses and/or may include multiple spacers betweenindividual tabs. The spacer and tab stacking sequence may be tailored toprovide for desired flexing/bending that reduces material stresses inthe interconnect and nearby electrode materials. In some examples, apredictive model may be employed to predict a desirable stackingsequence, e.g., using spacers of desired thicknesses. In some examples,the model may consider sources of variation in the components used tocreate the battery assembly. For example, the modeling may be used toassess the variation in thickness of the spacers and the associatedtabs. The model may be used to strategically place the spacers based oninferred variation or measured variation in each component of thestacked assembly.

Additionally, or alternatively, a battery assembly in accordance withsome examples of the disclosure may include a rivet through an aperturein the tab/spacer stack, (e.g., through a hole in or near the center ofthe stack of tabs). The rivet may prevent the mechanical “fanning” ofthe spacers. The rivet can be a piece of wire that is mechanicallyfastened and/or laser welded to the outer most plate tabs (e.g., the topand bottom tabs of the tab stack) of the stack assembly. The rivet maybe configured to counter-act the forces applied by the electrode stackexpansion.

Additionally, or alternatively, a battery assembly in accordance withsome examples of the disclosure may include one or more spacers (alsoreferred to as a shim) between the interconnect spacer tab stack and thesurrounding battery housing (e.g., between the top of the spacer tabstack and the surrounding battery housing). In some examples, the shimmay be formed of a polymer material that acts as an electrical insulatorto prevent electrical shorting. The shim consumes space between theinterconnect spacer stack and the enclosure wall, thus limiting the“fanning” that imparts stress on the laser welds. The shim may transferthe forces of electrode expansion away from the interconnect laser weldjoint and impart those forces to the more robust battery housing walls.

In some examples, the shim may be a relatively simple molded polymercomponent that is added during assembly, or it can be designed as anintegral feature of another insulator (e.g. headspace insulator, stackinsulator, and/or feedthrough insulator). In some examples, the “shim”may be attached as a foldable feature that allows assembly ease, whilealso preventing occurrences of the shim inadvertently not beinginstalled during battery assembly.

FIG. 1 is a conceptual diagram that illustrates an example medicaldevice system 10 that may be used to provide electrical therapy to apatient 12. Patient 12 ordinarily, but not necessarily, will be a human.System 10 may include an IMD 16, and an external device 24. In theexample illustrated in FIG. 1, IMD 16 has battery 26 positioned withinan outer housing 40 of the IMD 16. Battery 26 may be a primary orsecondary battery.

While the examples in the disclosure are primarily described with regardto battery 26 positioned within housing 40 of IMD 16 for delivery ofelectrical therapy to heart of patient 12, in other examples, battery 26may be utilized with other implantable medical devices. For example,battery 26 may be utilized with an implantable drug delivery device, animplantable monitoring device that monitors one or more physiologicalparameter of patient 12, an implantable neurostimulator (e.g., a spinalcord stimulator, a deep brain stimulator, a pelvic floor stimulator, aperipheral nerve stimulator, or the like), or the like. Moreover, whileexamples of the disclosure are primarily described with regard toimplantable medical devices, examples are not limited as such. Rather,some examples of the batteries described herein may be employed in anymedical device including non-implantable medical devices. For example,an example battery may be employed to supply power to a medical deviceconfigured delivery therapy to a patient externally or via atranscutaneously implanted lead or drug delivery catheter.

In the example depicted in FIG. 1, IMD 16 is connected (or “coupled”) toleads 18, 20, and 22. IMD 16 may be, for example, a device that providescardiac rhythm management therapy to heart 14, and may include, forexample, an implantable pacemaker, cardioverter, and/or defibrillatorthat provides therapy to heart 14 of patient 12 via electrodes coupledto one or more of leads 18, 20, and 22. In some examples, IMD 16 maydeliver pacing pulses, but not cardioversion or defibrillation shocks,while in other examples, IMD 16 may deliver cardioversion ordefibrillation shocks, but not pacing pulses. In addition, in furtherexamples, IMD 16 may deliver pacing pulses, cardioversion shocks, anddefibrillation shocks.

IMD 16 may include electronics and other internal components necessaryor desirable for executing the functions associated with the device. Inone example, IMD 16 includes one or more of processing circuitry,memory, a signal generation circuitry, sensing circuitry, telemetrycircuitry, and a power source. In general, memory of IMD 16 may includecomputer-readable instructions that, when executed by a processor of theIMD, cause it to perform various functions attributed to the deviceherein. For example, processing circuitry of IMD 16 may control thesignal generator and sensing circuitry according to instructions and/ordata stored on memory to deliver therapy to patient 12 and perform otherfunctions related to treating condition(s) of the patient with 1 MB 16.

IMD 16 may include or may be one or more processors or processingcircuitry, such as one or more digital signal processors (DSPs), generalpurpose microprocessors, application specific integrated circuits(ASICs), field programmable logic arrays (FPGAs), or other equivalentintegrated or discrete logic circuitry. Accordingly, the term“processor” and “processing circuitry” as used herein may refer to anyof the foregoing structure or any other structure suitable forimplementation of the techniques described herein.

Memory may include any volatile or non-volatile media, such as arandom-access memory (RAM), read only memory (ROM), non-volatile RAM(NVRAM), electrically erasable programmable ROM (EEPROM), flash memory,and the like. Memory may be a storage device or other non-transitorymedium.

The signal generation circuitry of 1 MB 16 may generate electricaltherapy signals that are delivered to patient 12 via electrode(s) on oneor more of leads 18, 20, and 22, in order to provide pacing signals orcardioversion/defibrillation shocks, as examples. The sensing circuitryof IMD 16 may monitor electrical signals from electrode(s) on leads 18,20, and 22 of 1 MB 16 in order to monitor electrical activity of heart14. In one example, the sensing circuitry may include switchingcircuitry to select which of the available electrodes on leads 18, 20,and 22 of 1 MB 16 are used to sense the heart activity. Additionally,the sensing circuitry of IMD 16 may include multiple detection channels,each of which includes an amplifier, as well as an analog-to-digitalconverter for digitizing the signal received from a sensing channel(e.g., electrogram signal processing by processing circuitry of theIMD).

Telemetry circuitry of 1 MB 16 may be used to communicate with anotherdevice, such as external device 24. Under the control of the processingcircuitry of IMD 16, the telemetry circuitry may receive downlinktelemetry from and send uplink telemetry to external device 24 with theaid of an antenna, which may be internal and/or external.

The various components of IMD 16 may be coupled to a power source suchas battery 26. Battery 26 may be a lithium primary battery or lithiumsecondary (rechargeable) battery although other types of batterychemistries are contemplated. Battery 26 may be capable of holding acharge for several years. In general, battery 26 may supply power to oneor more electrical components of IMD 16, such as, e.g., the signalgeneration circuitry, to allow IMD 16 to deliver therapy to patient 12,e.g., in the form of monitoring one or more patient parameters, deliveryof electrical stimulation, or delivery on a therapeutic drug fluid.Battery 26 may include a lithium-containing anode and cathode includingan active material that electrochemically reacts with the lithium withinan electrolyte to generate power. A wide variety of battery types and

Leads 18, 20, 22 that are coupled to IMD 16 may extend into the heart 14of patient 12 to sense electrical activity of heart 14 and/or deliverelectrical therapy to heart 14. In the example shown in FIG. 1, rightventricular (RV) lead 18 extends through one or more veins (not shown),the superior vena cava (not shown), and right atrium 30, and into rightventricle 32. Left ventricular (LV) coronary sinus lead 20 extendsthrough one or more veins, the vena cava, right atrium 30, and into thecoronary sinus 34 to a region adjacent to the free wall of leftventricle 36 of heart 14. Right atrial (RA) lead 22 extends through oneor more veins and the vena cava, and into the right atrium 30 of heart14. In other examples, IMD 16 may deliver therapy to heart 14 from anextravascular tissue site in addition to or instead of deliveringtherapy via electrodes of intravascular leads 18, 20, 22. In theillustrated example, there are no electrodes located in left atrium 36.However, other examples may include electrodes in left atrium 36.

IMD 16 may sense electrical signals attendant to the depolarization andrepolarization of heart 14 (e.g., cardiac signals) via electrodes (notshown in FIG. 1) coupled to at least one of the leads 18, 20, and 22. Insome examples, IMD 16 provides pacing pulses to heart 14 based on thecardiac signals sensed within heart 14. The configurations of electrodesused by IMD 16 for sensing and pacing may be unipolar or bipolar. IMD 16may also deliver defibrillation therapy and/or cardioversion therapy viaelectrodes located on at least one of the leads 18, 20, and 22. IMD 16may detect arrhythmia of heart 14, such as fibrillation of ventricles 32and 36, and deliver defibrillation therapy to heart 14 in the form ofelectrical shocks. In some examples, IMD 16 may be programmed to delivera progression of therapies (e.g., shocks with increasing energy levels),until a fibrillation of heart 14 is stopped. IMD 16 may detectfibrillation by employing one or more fibrillation detection techniquesknown in the art. For example, IMD 16 may identify cardiac parameters ofthe cardiac signal (e.g., R-waves, and detect fibrillation based on theidentified cardiac parameters).

In some examples, external device 24 may be a handheld computing deviceor a computer workstation. External device 24 may include a userinterface that receives input from a user. The user interface mayinclude, for example, a keypad and a display, which may be, for example,a cathode ray tube (CRT) display, a liquid crystal display (LCD) orlight emitting diode (LED) display. The keypad may take the form of analphanumeric keypad or a reduced set of keys associated with particularfunctions. External 24 can additionally or alternatively include aperipheral pointing device, such as a mouse, via which a user mayinteract with the user interface. In some embodiments, a display ofexternal 24 may include a touch screen display, and a user may interactwith programmer 24 via the display.

A user, such as a physician, technician, other clinician or caregiver,or the patient, may interact with external device 24 to communicate withIMD 16. For example, the user may interact with external device 24 toretrieve physiological or diagnostic information from IMD 16. A user mayalso interact with external device 24 to program IMD 16 (e.g., selectvalues for operational parameters of IMD 16).

External device 24 may communicate with IMD 16 via wirelesscommunication using any techniques known in the art. Examples ofcommunication techniques may include, for example, low frequency orradiofrequency (RF) telemetry, but other techniques are alsocontemplated. In some examples, external device 24 may include acommunication head that may be placed proximate to the patient's bodynear the IMD 16 implant site in order to improve the quality or securityof communication between IMD 16 and external device 24.

In the example depicted in FIG. 1, IMD 16 is connected (or “coupled”) toleads 18, 20, and 22. In the example, leads 18, 20, and 22 are connectedto IMD 16 using the connector block 42. For example, leads 18, 20, and22 are connected to IMD 16 using the lead connector ports in connectorblock 42. Once connected, leads 18, 20, and 22 are in electrical contactwith the internal circuitry of IMD 16. Battery 26 may be positionedwithin the housing 40 of IMD 16. Housing 40 may be hermetically sealedand biologically inert. In some examples, housing 40 may be formed froma conductive material. For example, housing 40 may be formed from amaterial including, but not limited to, titanium, stainless steel, amongothers.

FIG. 2 is a conceptual diagram of IMD 16 of FIG. 1 with connector block42 not shown and a portion of housing 40 removed to illustrate some ofthe internal components within housing 40. IMD 10 includes housing 40, acontrol circuitry 44 (which may include processing circuitry), battery26 (e.g., an organic electrolyte battery) and capacitor(s) 46. Controlcircuitry 44 may be configured to control one or more sensing and/ortherapy delivery processes from IMD 16 via leads 18, 20, and 22 (notshown in FIG. 2). Battery 26 includes battery assembly housing 50 andinsulator 48 (or liner) disposed therearound. Battery 26 chargescapacitor(s) 46 and powers control circuitry 44.

FIGS. 3 and 4 are conceptual diagrams illustrating aspect of examplebattery 26. Battery 26 includes assembly housing 50 having a bottomhousing portion 50A and top housing portion 50B (shown in FIG. 2), afeed-through terminal 56, and an electrode assembly 58. An electrolytemay be filled into via a fill port (not shown) in housing 50. Housing 50houses electrode assembly 58 with the electrolyte. Top portion 50B andbottom portion 50A of housing may be welded or otherwise attached toseal the enclosed components of battery 26 within housing 50.Feed-through assembly 56, formed by pin 62 and insulator member/ferrule64, is electrically connected to jumper pin 60B. The connection betweenpin 62 and jumper pin 60B allows delivery of positive charge fromelectrode assembly 58 to electronic components outside of battery 26.

As noted above, a fill port (not shown) allows for the introduction ofliquid electrolyte to electrode assembly 58. The electrolyte creates anionic path between the anode(s) and the cathode(s) of electrode assembly58. The electrolyte serves as a medium for migration of ions between theanode(s) and the cathode(s) during an electrochemical reaction withthese electrodes.

Electrode assembly 58 is depicted as a stacked assembly. The anode(s)comprise a set of electrode plates 72 (including individual anodeelectrode plate 76A) with a set of tabs 76 (including individual tab76A) extending therefrom that are conductively coupled via a conductivecoupler 80 (also referred to as an anode collector). Although notlabeled, the one or more spacers (e.g., conductive spacers) may belocated between respective tabs in the set of tabs 76. The conductivecoupler 80 may be a pin that extends vertically through the set of tabs76 and spacers located between respective tabs. Additionally, oralternatively, one or more welds 90 may also conductively couple the setof tabs 76 and spacers. In accordance with at least some of examples ofthe disclosure, as described below, conductive coupler 80 may be a rivetthat extends vertically through set of tabs 76 and spacers that alsomechanically attaches the individual tabs 76 and spacers to each other.

Each anode electrode plate 72A includes a current collector or grid 82,a tab 76A extending therefrom, and an electrode material. The electrodematerial (or anode material) may include elements from Group IA, IIA orIIIB of the periodic table of elements (e.g. lithium, sodium, potassium,etc.), alloys thereof, intermetallic compounds (e.g. Li—Si, Li—B,Li—Si—B etc.), or an alkali metal (e.g. lithium, etc.) in metallic form.

Cathode tabs 68 may be constructed in a similar manner as anode tabs 66.The cathodes include a set of electrode plates 74 (including individualcathode electrode plates 74A) with a set of tabs 78 (includingindividual tab 78A) extending therefrom. As labelled in FIG. 5, e.g.,one or more spacers (e.g., conductive spacers 86A-86C) may be locatedbetween respective tabs in the set of tabs 78. The conductive coupler 84connects the set of tabs 78 and spacers 86. Conductive coupler 84 orother cathode collector may be connected to conductive member 60A.Conductive member 60A, shaped as a spacer plate, may comprise titanium,aluminum/titanium clad metal or other suitable materials. Conductivemember 60A allows cathode tabs 68 to be electrically coupled toelectronic components outside of battery 26. Each tab of the set of tabs78 (including, e.g., individual tab 78A) may be additionally, oralternatively, attached to each other via laser weld(s) 92.

In accordance with at least some of examples of the disclosure, asdescribed below, conductive coupler 84 may be a rivet that extendsvertically through set of tabs 78 and spacers 86 that also mechanicallyattaches the individual tabs 76 and spacers 86 to each other.

Each cathode electrode plate 74A includes a current collector (notshown) or grid, an electrode material and a tab 78A extending therefrom.Tab 78A comprises conductive material (e.g., aluminum, etc.). Tab 78Acomprises conductive material (e.g., copper, titanium, aluminum, etc.).Electrode material (or cathode material) may include metal oxides (e.g.,vanadium oxide, silver vanadium oxide (SVO), manganese dioxide, etc.),carbon monofluoride and hybrids thereof (e.g., CFx+MnO2), combinationsilver vanadium oxide (CSVO), lithium ion, other rechargeablechemistries, or other suitable compounds.

FIG. 5 is a conceptual schematic diagram illustrating a magnified viewof a portion of cathode tabs 68 of battery 26. FIG. 6 is a cross-sectionview of the stack of cathode tabs 78 shown in FIG. 5. As shown,electrodes plates 74 of cathode 66 includes cathode electrode plates74A, 74B, 74C (among others) in a stacked configuration. Cathode tabs78A, 78B, 78C extend from cathode electrodes plates 74A, 74B, 74C,respectively, and exhibit the same stacked configuration as electrodeplate 74. At least one spacer is located between each respective tab.For example, spacer 86A is located between tabs 78A and tab 78B, and twospacers 86B and 86C are located between tab 78B and tab 78C.

For ease of description and illustration, not all the tabs and spacersof cathode stack 68 are labelled in FIGS. 5 and 6. However, it isunderstood that the description of tabs 78A-78C and spacers 86A-86C alsomay apply to any of the tabs and spacers shown in FIGS. 5 and 6.Additionally, while FIG. 5 is described with regard to cathode stack 68it is contemplated that the same configuration is applicable to anodestack 66 of battery 26 shown in FIG. 3.

In some examples, spacer 86A ensures tabs 78A and 78B are substantiallystraight extending from plates 74A and 74B, respectively, and are notbent during a subassembly process to connect the set of tabs 78(including, e.g., individual tab 78A) for cathode stack 68. While asingle spacer 86A is depicted as being placed between two tabs, morethan one spacer may be placed between two tabs, such as, e.g., spacers86B and 86C between tabs 78B and 78C.

Spacers 86A-86C may comprise a conductive material, e.g., such that theeach of the tabs are electrically interconnected. For electrode platesrelated to anode stack 66, titanium and alloys thereof or other suitablematerials are used. For electrode plates related to cathode stack 68,titanium, nickel, aluminum, alloys thereof or other suitable materialsare used.

Spacers 86A-86C may include a variety of shapes. Exemplary spacersinclude a substantially H-shaped spacer, substantially rectangular,circular, or include at least one triangular shape (e.g. a singletriangle, a hexagon etc.). Spacers 86A-86C may have different orsubstantially the same individual thicknesses in the z-direction labeledin FIG. 5, e.g., to achieve different design criteria. For example, athicker electrode plate may requires a thicker spacer. In the example inof FIG. 5, spacer 86A may have substantially the same thickness ofspacer 86B but spacer 86C may be thinner than spacers 86A and 86B. Insome examples, the thickness of a spacer may range from about 0.005inches to about 0.030 inches although other values are contemplated.Examples of spacers 86A-86C may include one or more of the examplespacers described in U.S. Published Patent Application 2009/0197180.

In some examples, the number of spacers and thicknesses of theindividual spacer(s) between the tabs of cathode stack 68 and anodestack 66 may be selected such that tab bending is minimized yet stillfits in the battery housing 50.

As shown in FIGS. 5 and 6, cathode stack 68 may include rivet 84extending through aperture 94 (shown in FIG. 4) that runs through theset of cathode tabs 78 (including, e.g., individual tab 78A), spacers86, and conductive plate 60A in the z-direction. Rivet 84 includes body96, head 100, and deformed tail 98. Body 96 may be a solid body (e.g.,as shown in FIG. 6) or a body that include an inner lumen (e.g., asshown in FIG. 8). Head 100 has a flanged portion that is located belowconductive plate 60A. Similarly, deformed tail 98 has a flanged portionthat is located above tab 78A, which is the “top” tab of the stack. Inthe example of FIGS. 5 and 6, spacer 86D is between tail 98 and tab 78A.In such an example, spacer 86D may be thicker and other morestructurally rigid than tab 78A, e.g., to prevent head 98 of rivet 84from “pulling-through” tab 78A if spacer 86D was not present. In otherexamples, tail 98 may be directly adjacent to tab 78A.

The flanged shape of head 100 and deformed tail 98 allows rivet 84 tofasten or otherwise mechanically attach cathode tabs 78, spacers 86, andconductive plate 60A to each other and prevent the stack from becomingdetached from each other. As will be described in further detail below,before being deformed, tail 98 may be inserted into aperture 94 suchthat it extends out of the top of the stack of tabs 78, spacers 86, andconductive plate 60A. Subsequently, tail 98 is deformed to form theflange and attaches the stack of tabs 78, spacers 86, and conductiveplate 60A together.

Rivet 84 may fix and define the thickness of the stack of tabs 78,spacers 86, and conductive plate 60A shown in the z-direction tocorrespond to the thickness of body 96 in the z-direction. In someexamples, rivet 84 may apply a compressive force between head 100 andtail 98, e.g., to counteract a force in the other direction that wouldotherwise cause tabs 78 and spacers 86 from separating. In this manner,the stack of tabs 78 are prevented, e.g., from “fanning,” e.g.,spreading apart in the z-direction, during the operating life of battery26 and preventing tabs 78 from losing electrical interconnect betweeneach other.

In some examples, rivet 84 is configured to keep the stack of tabs 78together such that weld(s) 92 does not receive the “book opening”mechanical loading. Weld(s) 92 may be present in assemblies includingrivet 84 in stack of tabs 78 to provide a robust electrical connection,e.g., between the respective tabs. Long-term, corrosion and surfaceoxidation may degrade the interface contacts, thus, the need for theweld.

In some examples, the height (in the Z-direction) of rivet 84 isselected based on the stack modeling described above. The modeling workmay suggest just one rivet for all production variation options, or iftoo variable, the individual tab/spacer stacks can be actively measuredduring manufacturing before selecting any of several premade rivetheights for a particular stack.

Rivet 84 may be formed from any suitable material such as stainlesssteel (e.g., 300 series stainless steel), monel or other nickel-copperalloy, and/or nickel. In some examples, rivet 84 may be an electricallyconductive material such that rivet 84 functions to electrically couplethe individual tabs 78, spacers 86, and conductive plate 60A together,e.g., alone or in combination with other features such as welds 92and/or conductive spacers 86. In other examples, rivet 84 may be formedof an electrically insulating material.

FIG. 7 is a photograph illustrating example rivet 84 that may beemployed in examples of the disclosure. Rivet 84 include head 100, tail98, and body 96 that extends between head 100 and tail 98. Rivet 84 isshown in a state prior to tail 98 being deformed as shown in FIG. 6, forexample. Body 96 of rivet 84 has an outer diameter D that is smallerthan the size of aperture 94 extending through the stack of tabs 78,spacers 86, and conductive plate 60A shown in FIGS. 5 and 6. In someexamples, body 96 of rivet 85 may have an outer diameter of about 28mils or less, e.g., with the diameter of head 100 and deformed tail 98being about 40 mils or greater. In examples in which body 96 includes aninner lumen rather than being solid, the thickness of the body walls maybe about 5 mils. In some examples, the overall length of rivet 84 fromhead 100 to tail 98 may be about 272 mils or less. In some examples, theoverall height (in the Z-direction) of the combination of tabs 78 andspacers 86 may be about 0.230 inches (e.g., +/−0.03 inches). Othervalues are contemplated.

FIG. 8 is a schematic diagram illustrating an example apparatus 106 fordeforming tail 98 when arranged with cathode tabs 78 and spacers 86 toform a stacked assembly in which tabs 78 and spacers 86 are attached toeach other via rivet 84. FIG. 9 is a flowchart illustrating an exampletechnique for attaching tabs 78 and spacers 86 to each other via rivet84. For ease of description, the example technique of FIG. 9 will bedescribed with regard to apparatus 106 shown in FIG. 8.

As shown in FIG. 9, tabs 78 and spacers 86 may be stacked on body 96 ofrivet 84 (102). For example, aperture 94 of the individual tabs of tabs78 and individual spacers 86 may be sequentially placed over tail 98onto body 96 in the order and arrangement desired, e.g., in thearrangement shown in FIG. 8. In other examples, tabs 78 and spacers 86may be arranged in a stack initially with apertures aligned (e.g., usinga fixture pin) and then placed as a single stack onto body 96 over tail98. The stacking may be accomplished manually or by robotic assemblydevices (e.g., a pick and place robotic device).

Once tabs 78 and spacers 86 are assembled over rivet 84, tail 98 may bedeformed to attach tabs 78 and spacers 86 in the stacked arrangement(104). For example, retractable supports 110 may be used force swage 108into tail 98 against fixed pin 112, e.g., via a compressive force, todeform the edges of tail 98 outwardly and form a flanged end as shown inFIG. 8. In some example, weld(s) 92 may then be formed, e.g., via laserwelding or other suitable process, in tabs 78 and spacers 86 after rivet84 has been installed. Alternatively, weld(s) 92 may be formed prior toinstallation of rivet 84.

The example of FIG. 9 illustrates only one example technique fordeforming tail 98 of rivet 84 within aperture 94 in the stack of tabs 78and spacers 86 to attach tabs 78 and spacers 86 to each other. Otherexamples suitable technique may be employed as well as other types ofrivets, such as, e.g., rivets with solid bodies.

As noted above, some example battery assemblies of the disclosure mayadditionally, or alternatively, include a shim on the “top” of the stackof tabs 78 and spacers 86, e.g., to prevent “fanning” of the tabs 78 asdescribed herein. FIG. 10 is a schematic diagram illustrating an exampleof battery 26 including shim 114. As shown in FIG. 10, shim 114 islocated on stack of tabs 78 and spacers 86 of cathode stack 68. In theexample of FIG. 10, shim 114 is not directly on top of tab 78A butinstead is separated from tab 78A by spacer 86D. In other examples, shim114 may be located directly on tab 78A. Although not shown in FIG. 10,in some examples, welds 92 may be extended to include shim 114 along theside of the stack assembly depending on the material used to form shim114.

Additionally, shim 114 is located on stack of tabs 76 of anode stack 66in a similar fashion. Shim 114 is a single member that spans gap 116between stack of tabs 78 of cathode stack 68 and stack of tabs 76 ofanode stack 66, which also includes spacers (not labelled) between theindividual tabs in the stack. While shim 114 is a single member in theexample of FIG. 10, in other examples, battery 26 may include one shimlocated on the stack of tabs and spacers for cathode stack 68 andanother shim located on the stack of tabs and spacers for anode stack66.

In some examples, rather than being a separate component, shim 114 maybe included as an integral feature of another component, e.g., of aninsulative component. For example, in some examples, shim 114 may be aportion of another typical insulator used to isolate electricalpolarities within the battery 26, e.g., a headspace insulator, a stackinsulator, and/or a feedthrough insulator. In some examples, shim 114may be attached or otherwise included as a foldable feature of thecomponent to allow for ease of assembling battery 26, while alsopreventing against the occurrence of inadvertently not being installedduring the assembly of battery 26.

Although not shown in FIG. 10, when battery housing 50 is assembled withtop portion 50B (shown in FIG. 2) and bottom portion 50A being sealed orotherwise attached to each other to form housing 50, the thickness ofshim 114 (in the z-direction) may be selected such that the top surfaceof shim 114 comes into contact with the inner surface of top portion 50Bof battery housing 50. In some examples, the contact between the topsurface of shim 114 and the inner surface of top portion 50B of housing50 may apply a compressive force (represented by arrows 120 in FIG. 10)or otherwise prevent cathode stack 68 and anode stack 66 from fanning.For example, when top portion 50B is attached to bottom portion 50A ofhousing 50, e.g., via a weld around the perimeter of housing 50 at theinterface between top and bottom portion 50B and 50B, compressive force120 may be applied to the stack of tabs 78 of cathode 68 and the stackof tab 76 of anode 66 between the top and bottom portions 50B and 50A byway of shim 114. In this manner, compressive force 120 may prevent thestack of tabs 78 of cathode 68 and the stack of tab 76 of anode 66 from“fanning,” e.g., during the operating life of battery 26.

Shim 114 may be formed of any suitable material. In some examples, shim114 may be formed of an electrically insulating material, e.g., toprevent electrical coupling of cathode stack 68 and anode stack 66 byway of shim 114 and/or electrical coupling of cathode stack 68 and/oranode stack 66 to housing 50. Example insulating materials may includepolypropylene, polyethylene, and/or the like. In other example, shim 114may be formed of an electrically conductive material, such as titanium,stainless steel, and/or the like. In some examples, spacer 86D betweentop tab 78A of cathode 68 as well as the spacer between shim 114 and toptab 76A of anode 66 may be electrically insulating to prevent electricalcoupling between the respective electrode tabs and shim 114. In otherexamples, shim 114 may be configured such that the compressive force isapplied once the cathode stack 68 and/or anode stack 66 begin to startfanning, e.g., at some point during the operating life of battery 26.

FIG. 11 is a schematic diagram illustrating an example of shim 114. Asshown, shim 114 does not have a constant thickness but instead exhibitsa thickness T1 on one side of shim 114 and thickness T2 on the otherside of shim 114. This difference in this may account for thedifferences in distance between the tab/spacer stack of cathode stack 68and the inner surface of top portion 50B of housing 50 compared to thedistance between the tab/spacer stack of anode stack 66 and the innersurface of top portion 50B of housing 50 when housing 50 is assemblyaround the internal components of battery 26.

As shown, in some examples, shim 114 may include posts 122A and 122B.Post 122A may be configured to fit within a portion of aperture 94 ofthe stack of tabs 78 and spacers 86 of cathode stack 68. Similarly, post122B may be configured to fit within a portion of a similar aperture inthe stack of tabs/spacers of anode stack 66. This feature may facilitatethe registration or alignment of shim 114 with respect to anode stack 66and cathode stack 68, and maintain shim 114 in place, e.g., before,during, and/or after top portion 50B and bottom portion 50A of housing50 are assembled. Such a design may be utilized in cases in which arivet, such as, rivet 84, does not extend through the stack of tabs andspacers of the anode stack and cathode stack. For examples including arivet in one or both of the anode stack and cathode stack, shim 114 mayinclude another type of registration feature (e.g., indentions into shim114 rather than protrusion such as posts 122A and 122B) other than thatshown in FIG. 11, e.g., so that the rivet and shim may both preventfanning of the stack of tabs during the operating life of the battery.

FIG. 12 is a conceptual diagram illustrating another example battery126. Battery 126 may be similar to the other battery assembliesdescribed herein and like features are numbered similarly. FIG. 12illustrates an example in which shim 114 is employed between the innersurface of the top portion 50B of housing 50 and cathode stack 68 andanode stack 66. As described above, the contact between the top surfaceof shim 114 and the inner surface of top portion 50B of housing 50 mayapply a compressive force (represented by the two arrows in FIG. 12) orotherwise prevent cathode stack 68 and anode stack 66 from fanning. Forexample, when top portion 50B is attached to bottom portion 50A ofhousing 50, e.g., via a weld around the perimeter of housing 50 at theinterface between top and bottom portion 50B and 50B, the compressiveforce may be applied to the stack of tabs 78 of cathode 68 and the stackof tab 76 of anode 66 between the top and bottom portions 50B and 50A byway of shim 114. In this manner, the compressive force may prevent thestack of tabs 78 of cathode 68 and the stack of tab 76 of anode 66 from“fanning,” e.g., during the operating life of battery 126. In someexamples, shim 114 may be configured such that the compressive force isapplied once the cathode stack 68 and/or anode stack 66 begin to startfanning, e.g., at some point during the operating life of battery 126.

Various examples have been described in the disclosure. These and otherexamples are within the scope of the following clause and claims.

Clause 1. A battery assembly for an implantable medical device, theassembly comprising: an electrode stack comprising a plurality ofelectrode plates, wherein the plurality of electrode plates comprises afirst electrode plate including a first tab extending from the firstelectrode plate and a second electrode plate including a second tabextending from the second electrode plate; a spacer between the firsttab and the second tab; and

a rivet extending through the first tab, second tab, and spacer, whereinthe rivet is configured to mechanically attach the first tab, secondtab, and spacer to each other.

Clause 2. The assembly of clause 1, wherein the rivet comprises a flaredhead, a deformed tail, and a rivet body extending between the flaredhead and deformed tail, and wherein the flared head is on a first sideof the electrode stack, and the deformed tail on a second side of theelectrode stack.

Clause 3. The assembly of clause 1, wherein the spacer comprises a firstspacer, wherein the plurality of electrode plates includes a thirdelectrode plate including a third tab extending from the third electrodeplate, wherein the second tab is between the first tab and the thirdtab, the assembly further comprising a second spacer between the thirdtab and the second tab, wherein the rivet extends through the third taband the second spacer.

Clause 4. The assembly of clause 3, wherein the first spacer has a firstthickness different from a second thickness of the second spacer.

Clause 5. The assembly of clause 1, wherein the spacer comprises a firstspacer, the assembly further comprising a second spacer between thefirst tab and second tab adjacent the first spacer.

Clause 6. The assembly of clause 1, further comprising a weld on theelectrode stack extending from the first tab to the second tab acrossthe spacer.

Clause 7. The assembly of clause 1, wherein the first electrode plate isthe top plate in the plurality of electrode plates of the electrodestack, the assembly further comprising: a battery housing that enclosesthe electrode stack; and a shim located on top of the first tab betweenthe first tab and an inner surface of the battery housing.

Clause 8. The assembly of clause 7, wherein the first electrode platecomprises a first anode plate and the second electrode plate comprises asecond anode plate, wherein the plurality of electrode plates furthercomprises a first cathode plate including a third tab extending from thefirst cathode plate and a second cathode plate including a fourth tabextending from the second cathode plate, wherein the third tab andsecond tab are stacked adjacent to the first tab and second tab, andwherein the top spacer spans a gap between the first tab and the thirdtab.

Clause 9. The assembly of clause 7, wherein the top spacer is formed ofan electrically insulative material to electrically isolate the firsttab from the battery housing.

Clause 10. A battery assembly for an implantable medical device, theassembly comprising: a battery housing; an electrode stack comprising aplurality of electrode plates, wherein the plurality of electrode platesincluding a first tab stack of anode tabs extending from anode plates ofthe electrode stack and a second tab stack of cathode tabs extendingfrom cathodes plates of the electrode stack, wherein the first tab stackis adjacent to the second tab stack and a gap separates the first tabstack from the second tab stack; and a shim located on a top tab of atleast one of the first tab stack or the second tab stack, wherein theshim is located between the at least one of the first tab stack or thefirst tab of the second tab stack and the battery housing.

Clause 11. The battery assembly of clause 10, wherein the shim spans thegap between the first tab stack and the second tab stack.

Clause 12. The assembly of clause 10, wherein the shim is formed of anelectrically insulative material to electrically isolate the first tabstack and the second tab stack from the battery housing.

Clause 13. The assembly of clause 10, wherein the battery housing isconfigured to apply a compressive force to the first tab stack and thesecond tab stack via the shim.

Clause 14. The assembly of clause 10, wherein the second tab stackincludes a first cathode tab and a second cathode tab, the assemblyfurther comprising a first spacer located between the first cathode taband the second cathode tab.

Clause 15. The assembly of clause 14, further comprising a second spacerbetween the first cathode tab and the second cathode tab, and whereinthe first spacer has a thickness less than a thickness of the secondspacer.

Clause 16. The assembly of clause 14, wherein the second tab stackincludes a third cathode tab, the assembly further comprising a secondspacer between the second cathode tab and the third cathode tab.

Clause 17. The assembly of clause 16, wherein the first spacer has athickness less than a thickness of the second spacer.

Clause 18. The assembly of clause 10, further comprising a rivetextending through the second tab stack to mechanically attach theindividual tabs of the second tab stack to each other.

Clause 19. The assembly of clause 18, wherein the rivet comprises aflared head, a deformed tail, and a rivet body extending between theflared head and deformed tail, and wherein the flared head is on a firstside of the second tab stack, and the deformed tail on a second side ofthe second tab stack.

Clause 20. The assembly of clause 10, further comprising a weld on thesecond tab stack extending from a top tab of the second tab stack to abottom tab of the second tab stack.

Clause 21. The assembly of clause 10, wherein the weld extends to theshim. Clause 22. The assembly of clause 10, wherein the shim includes afirst protrusion configured to mate with an aperture in the first tabstack and a second protrusion configured to mate with an aperture in thesecond tab stack.

Clause 23. The assembly of clause 10, wherein the shim is configured totransfer a compressive force from battery housing to the at least one ofthe first tab stack or the second tab stack.

Clause 24. An implantable medical device comprising: an outer housing;processing circuitry; and the battery assembly of clause 1 within theouter housing, wherein the processing circuitry is configured to controldelivery electrical therapy from the implantable medical device to apatient using power supplied by the battery assembly.

Clause 25. An implantable medical device comprising: an outer housing;

processing circuitry; and the battery assembly of clause 10 within theouter housing, wherein the processing circuitry is configured to controldelivery electrical therapy from the implantable medical device to apatient using power supplied by the battery assembly.

Clause 26. A method comprising assembling any one of clauses 1-25.

The invention claimed is:
 1. A battery assembly for an implantablemedical device, the assembly comprising: an electrode stack comprising aplurality of electrode plates, wherein the plurality of electrode platescomprises a first electrode plate including a first tab extending fromthe first electrode plate and a second electrode plate including asecond tab extending from the second electrode plate; a spacer betweenthe first tab and the second tab; and a rivet extending through thefirst tab, second tab, and spacer, wherein the rivet is configured tomechanically attach the first tab, second tab, and spacer to each other.2. The assembly of claim 1, wherein the rivet comprises a flared head, adeformed tail, and a rivet body extending between the flared head anddeformed tail, and wherein the flared head is on a first side of theelectrode stack, and the deformed tail on a second side of the electrodestack.
 3. The assembly of claim 1, wherein the spacer comprises a firstspacer, wherein the plurality of electrode plates includes a thirdelectrode plate including a third tab extending from the third electrodeplate, wherein the second tab is between the first tab and the thirdtab, the assembly further comprising a second spacer between the thirdtab and the second tab, wherein the rivet extends through the third taband the second spacer.
 4. The assembly of claim 3, wherein the firstspacer has a first thickness different from a second thickness of thesecond spacer.
 5. The assembly of claim 1, wherein the spacer comprisesa first spacer, the assembly further comprising a second spacer betweenthe first tab and second tab adjacent the first spacer.
 6. The assemblyof claim 1, further comprising a weld on the electrode stack extendingfrom the first tab to the second tab across the spacer.
 7. The assemblyof claim 1, wherein the first electrode plate is the top plate in theplurality of electrode plates of the electrode stack, the assemblyfurther comprising: a battery housing that encloses the electrode stack;and a shim located on top of the first tab between the first tab and aninner surface of the battery housing.
 8. The assembly of claim 7,wherein the first electrode plate comprises a first anode plate and thesecond electrode plate comprises a second anode plate, wherein theplurality of electrode plates further comprises a first cathode plateincluding a third tab extending from the first cathode plate and asecond cathode plate including a fourth tab extending from the secondcathode plate, wherein the third tab and second tab are stacked adjacentto the first tab and second tab, and wherein the top spacer spans a gapbetween the first tab and the third tab.
 9. The assembly of claim 7,wherein the top spacer is formed of an electrically insulative materialto electrically isolate the first tab from the battery housing.